The Golden Eagle is a large, dark, long-winged raptor that soars on flat or slightly up-tilted wings. In all ages except newly fledged juveniles, and especially in adult plumage, the nape feathers create a "golden" hue found in no other species of raptor. The sexes are similar, and in flight, the adults are essentially all dark with no light markings. The juveniles, immatures, and sub-adults resemble the adults in that they are large, dark raptors, but the base of the primaries and the base of the tail are boldly whitish and contrast markedly with the rest of the plumage. It is mainly a bird of the open country that prefers to nest on cliffs or in very large trees. It hunts largely by soaring and feeds on small mammals, birds, and carrion, and has been unjustifiably persecuted for allegedly causing great losses to the livestock industry through predation of young animals. The legs are feathered to the toes.
SIZE
The Golden Eagle is a large raptor exceeded in size in North America only by the California Condor and the Bald, Steller's, and White-tailed eagles. The female averages larger than the male but there is overlap in some measurements. Combined length measurements for males and females range from 30 to 40 inches (76.2 to 101.6 centimeters). The combined wingspread ranges from 60 to 80 inches (152.4 to 203.2 centimeters). Weights for males vary from 6.5 to 9.5 pounds (3.0 to 4.3 kilograms) with an average 8.6 pounds (3.9 kilograms) and females from 8 to 13 pounds (3.6 to 5.9 kilograms) with an average of 10.6 pounds (4.8 kilograms). Birds in their first year of life weigh as much as the adults.
MORPHS AND MOLTS
There are no color-morphs of Golden Eagle. There is however, a juvenile plumage followed by three or four "subadult", or pre-definitive plumages prior to the "adult", or definitive plumage developing. Incomplete molts result in various feathers always present from previous plumage generations such that some birds may never acquire pure, complete definitive feathering. The molt is prolonged and appears confusing, if not chaotic to understand in terms of the sequence of individual feather molt. For example, the primary flight feathers start molting from the innermost outward. After a few feathers are renewed, the molt ceases until the following year, beginning again where it left off, progressing outwards. Simultaneously, the molt can start again with the innermost primaries.
The juvenile plumage is acquired while the young are in the nest. It begins to appear about day 24 and covers the nestling by about day 56. The plumage is fully-grown by about 112 days. This plumage is retained throughout the winter and is then replaced by the first prebasic molt which begins at about month 11 and is prolonged. The first basic (immature) plumage is attained from spring into late summer of the year following hatching and is retained for about one year. The second basic plumage is attained from spring through late summer of the second year after hatching. It too is retained for almost one year. Birds in this plumage essentially look like adults. The third basic plumage is attained from spring through late summer of the third year after hatching and retained for one year. Again, it looks like the adult plumage. The fourth basic plumage is attained from spring through summer of the fourth year after hatching. This is the plumage that is repeated annually thereafter and is considered to be the first true definitive or "adult" plumage by some authors. Depending upon interpretation, the first true adult plumage is therefore not acquired until the fourth or fifth calendar year of life, even though by the third calendar year, birds may well look like adults in the field. The presence of earlier juvenile type feathers in this third year are difficult to detect under field conditions.
SPECIFIC DESCRIPTION
Adult Male - Flight
- adults appear as large, dark birds with wide, long wings
- the underside of the body and wings are not uniform dark brown but appear mottled due to old and new feathers
- the underside of the tail is dark with lighter narrow grayish banding evident in good lighting
- the top of the bird is all dark including the wings
- a tawny band through the coverts may be evident on the upper surface
- rarely, whitish patches or epaulettes may be seen on the shoulder areas of the upper wing
- the nape area stands out as being lighter, golden, or blondish and is distinctive at some distance
- the rear trailing edge of the wing indents where the wings join the body and the secondaries bulge rearward, giving the wing edge more of an "S" shape and the bird more of a narrow waisted look than in the Bald Eagle
- the head looks relatively small, appearing to be about one-third as long as the tail
- trailing edge of wing has wide dark band
- the wings may be held flat or in a sltrong dihedral when soaring, especially in high winds
- the wing beat is slow but more shallow than that of the Bald Eagle
Adult Female - Flight
- adults appear as large, dark birds with wide, long wings
- most will appear larger than males
- the underside of the body and wings are mottled with dark brown due to old and new feather pattern
- the underside of the tail is dark with lighter grayish banding evident in good lighting
- one narrow and one wide tail band
- the top of the bird is all dark including the wings
- a tawny band through the coverts may be evident on the upper surface
- rarely, whitish patches or epaulettes may be seen on the shoulder areas of the upper wing
- the nape area stands out as being lighter, golden, or blondish and is distinctive at some distance
- the rear trailing edge of the wing indents where the wings join the body and the secondaries bulge rearward, giving the wing edge more of an "S" shape and the bird more of a narrow waisted look than in the Bald Eagle
- the head looks relatively small, appearing to be about one-third as long as the tail
- the wings may be held flat or in a slight dihedral when soaring
- the wing beat is slow but more shallow than that of the Bald Eagle
Immature (first year) - Flight
- appears as a large, dark raptor with contrasting hackles just as adults do
- the body appears uniformly dark but the base of the tail is white set against a prominent dark terminal band
- the two-toned tail is visible on both the upper and lower surface
- the primaries may show large white patches on both the upper and lower surface. However, many immatures (first year) have little or no white in the wings.
- the overall impression from below is of a large, dark raptor with three apparent white patches in the outer wings and tail
- this contrasts with immature Bald Eagles that can show three white areas, but they are in the inner wings and tail area
- other flight traits are as for adults except that the tawny wing bar on the upper surface may not be present
Subadult (second to fourth year) - Flight
- in general, these birds appear similar to the juveniles
- as they become older and progress through the several molts of this period, the amount of white in the primaries becomes reduced as does the amount of white in the basal area of the tail
- due to individual variation and the potential to be in various stages of the subadult plumages, it is difficult to generalize about the amount of white that could be visible on any particular bird, but in general, any white in the tail or wings is indicative of the bird being four years old or less. Some individuals will retain white markings in the tail throughout their life however.
- the tawny diagonal bar on the upper wing surface is visible
- other flight traits are similar to the adults
SIMILAR SPECIES
In North America, the Golden Eagle might only reasonably be confused with some immature plumages of the Bald Eagle. The first-year Bald Eagle resembles the adult Golden Eagle, but lacks the lighter, "gold" hackles and has a larger, mono-toned dark beak as opposed to a two-toned beak. It also lacks the tawny stripe across the wing. The Bald Eagle has bare tarsi whereas the Golden Eagle has feathered ones. Other transition plumages of the immature Bald Eagle has some degree of white on the back and belly which is lacking in the Golden Eagle of any age. In flight, the Golden Eagle has dark axillars in all plumages whereas the Bald Eagle has some degree of white axillars during all of the immature plumages. By the time the Bald Eagle axillars become dark, the white head and tail has been acquired. In any plumage, the immature Bald Eagle has distinct white patches only in the first three primaries. Thus, any eagle without a white head with dark axillars or wing linings, is a Golden Eagle. Any eagle with white markings on the wing linings is a Bald Eagle, irrespective of head color.
At some distance, vultures and condors might be mistaken for a Golden Eagle due to their size and overall dark coloration. Their habit of soaring with their wings in a pronounced dihedral and rocking back and forth in flight distinguish them from the Golden Eagle. The latter species does not hold its wings as high and has a steady flight. Perched vultures have reddish heads on adults and gray heads on immatures in contrast with the brown and gold head of the eagle. The Black Vulture has bold white wing patches at the tips of the wings - a trait not shared by any plumage of the Golden Eagle. The Black Vulture holds its wings flat when soaring, but it is a much smaller bird than the Golden Eagle and the wings appear short and wide. The fanned tail is also very short and wide. The California Condor is no longer likely to be seen, but is extremely large and flies in level flight with little flapping. Large triangular white patches in the axillar area distinguish this endangered species from any plumage of the Golden Eagle. The tail of the Golden Eagle is proportionately longer than that of a condor and the eagle is significantly smaller.
OTHER NAMES
The Golden Eagle is also referred to as "Black Eagle", "Brown Eagle", "Dark Eagle", "Calumet Eagle", "Mountain Eagle", "Canadian Eagle", "Royal Eagle", "Ring-tailed Eagle", "War Eagle", and "Black Mexican Eagle."
ETYMOLOGY
The genus name Aquila is Latin for "eagle." The species name chrysaetos is Greek for "golden eagle" which is obtained from the combination of khrysos for "golden" and aetos for "eagle." Golden refers to the color of the feathering on the nape. Eagle is a restricted reference to certain large, superficially similar diurnal birds of prey but it does not necessarily imply evolutionary or genetic relationships.
MYTHOLOGY
The Golden Eagle occupies a prominent place in the legends and culture of many peoples. From myths, legends, taboos, rituals, aesthetic appreciation, totems and heraldry, the belief in the sacred values of this bird extends deep into the culture of our native North Americans. Eagle feathers were used in ceremonies and worn by people to ward off evil spirits, or to empower themselves with the strength of the eagle itself. War bonnets were made by some tribes and symbolize the relationship embodied there.
